1. Field of the Invention
The present invention relates to an image forming apparatus having a plurality of scanning type optical devices used in a copy machine, a printer, a facsimile, etc.
2. Related Background Art
Conventionally, in a scanning type optical device used in a laser beam printer (LBP), a digital copy machine, etc., light flux emitted from a light source means is light-modulated on the basis of an image signal and is periodically deflected by a deflector comprising, e.g., a rotary polygon mirror and then converged in a spot by a scanning type optical element (image forming element) having an fxcex8 characteristic onto a surface of a recording medium (photosensitive drum) having a photosensitivity, which surface is scanned optically to record the image.
FIG. 9 is a schematic diagram for showing an important part of the above-mentioned type of a conventional scanning type optical device.
In the scanning type optical device shown in FIG. 9, divergent light flux emitted from a light source means 91 is transformed by a collimator lens 92 into roughly parallel light flux, which is in turn limited in light quantity by a diaphragm 93 and then injected to a cylinder lens (cylindrical lens) 94 having a predetermined refracting power only in the sub-scanning direction. The roughly parallel light flux thus injected to the cylinder lens 94 is emitted as in a main scanning cross section, to be converged in a subscanning cross section and formed as an approximate line image on a reflecting surface 95a of a deflector 95 comprising a rotary polygon mirror.
Thus, the light deflected by (reflected from) the surface 95a of the deflector 95 passes through a scanning type optical element (fxcex8 lens) having an fxcex8 characteristic and is guided onto a photosensitive drum surface 98, which surface is then scanned optically in a direction of an arrow B when the deflector 95 is turned in a direction of an arrow A. In this way, an image is recorded on the photosensitive drum surface 98, which is a recording medium.
Recently, there has been proposed a color image forming apparatus having a plurality of (e.g., four) scanning type optical devices (see Japanese Patent Application Laid-Open Nos. 6-183056 and 10-186254).
A conventional color image forming apparatus, however, uses many folding mirrors and has a plurality of (e.g., four) scanning type optical devices independently screwed to a side plate of the main body thereof, so that when those optical devices are specifically fixed to that main body, their light application positions are deviated in different directions, thereby giving rise to misregistration in color, and thus causing image quality deterioration.
Furthermore, since they are solidly fixed in this manner, their light application positions are deviated in different directions by environmental fluctuations, i.e., high/low temperatures, distorted mounting (where the color image forming apparatus is mounted on a distorted surface), which also gives rise to misregistration in color.
It is an object of the present invention to provide an image forming apparatus for suppressing deviations in the application position of light emitted from an optical box, thus preventing an image from being deteriorated.
It is another object of the present invention to provide an image forming apparatus comprising an image bearing body, a light source, a polarizing means for polarizing light emitted from the light source, a lens for imaging light polarized by the polarizing means onto the image bearing body, and an optical box for containing at least the light source, the polarizing means, and the lens, wherein the optical box is provided plurally and the plurality of optical boxes to be integrated.
Further objects of the present invention will become apparent from the following description.